1. Technical Field
The present invention relates to recording devices such as facsimile machines and printers.
2. Related Art
An ink jet printer, which is an example of a recording device, will hereinafter be described. An example of an ink jet printer is a so-called serial type printer in which an ink jet recording head that ejects ink onto paper, which is an example of a medium, is mounted on a carriage reciprocatable in a paper width direction (a main scanning direction), which is a direction intersecting a paper transport direction. The serial type ink jet printer performs recording on paper while alternately performing a main scanning movement of the carriage and a predetermined amount of paper transport movement (note that the main scanning movement of the carriage and the paper transport movement may be performed at the same time).
A controller which controls a motor which drives a carriage performs PID control in accordance with a deviation of an actual speed value of the carriage from a target speed value, which is obtained by a subtractor. In PID control, for example, a drive current of the motor is controlled so that the motor is accelerated or decelerated in accordance with an acceleration curve and a deceleration curve based on a predetermined target speed table. In such PID control, coefficients (gains) for a proportional term (P), an integral term (I), and a derivative term (D) are adjusted for optimal control (see, for example, Japanese patent No. 4009834).
The ink jet printer is usually placed on a flat surface but may be placed on a sloping surface in some cases. In particular, a small, lightweight, and portable recording device may be often used while not being horizontal. In such a case, paper may be transported while being excessively slanted, which may cause defective paper transport.
In addition, in such a case, a driving load on a carriage may vary between back and forth movements. For example, in the case where the device is tilted in a manner such that a forward movement of the carriage goes up a slope and a backward movement goes down the slope, the driving load of the former is larger than that of the latter. As a result, for example, in the backward movement (when the carriage goes down the slope), the carriage may stop beyond a target position, causing an inappropriate recording result.
A sensor dedicated to detecting the tilt of the device could be provided in order to solve the above problem; however, this unfavorably increases the cost of the device. This technical problem is not taken into consideration in the ink jet printer described in Japanese Patent No. 4009834.